1. Field of the Invention
This invention pertains to the field of electrical measuring and testing by the use of especially constructed probes or measuring electrodes. More particularly, the present invention relates to apparatus and methods of providing a temporary electrical interface between test equipment intended for obtaining static and/or dynamic information from electric signals and electrical test points as on printed circuit boards and integrated circuit chips.
2. Description of the Prior Art
Electrical connections for measurement, testing and signal acquisitions from early electronic components and circuits were frequently established by relatively blunt probes and/or spring biased jaws (sometimes called alligator clips) attached to wires. As the size of the electrical contacts diminished with miniaturization of circuits and integrated circuit chips developed, the clip connectors likewise diminished in size and needle point probes became popular. The advent of contemporary circuit chips necessarily has resulted in extremely small, high density electrical connections. It has become difficult, and sometimes impossible, to establish and maintain electrical contact on such connections by use of even miniaturized clips and needle probes.
The more recent art of electrical measuring and testing includes a number of devices for facilitating connection to test pads of printed circuits and the like. Thus, much of the prior art is predominantly directed to structure wherein probes are incorporated in automated test equipment rather than adapted for a tool suitable for manual use, such as by an electronics technician. Such devices have employed spring biased contactors to ensure continuous electrical contact despite variations in the closure force applied between the tool and the product under test.
For example, U.S. Pat. No. 4,151,465 by Lenz describes a test probe for use with microelectronic circuits wherein the test probe is provided with means for varying the pressure of a contact tip against the terminal pads of an electronic circuit under test. The probe of this device includes a flexible neck portion on whose end the contact tip is mounted. This flexible neck portion is provided with transverse slots into which flexible inserts are selectively inserted in order to control the tip pressure of the contact tip. The contact tip comprises a sleeve, a contact needle and a conductive lead.
U.S. Pat. No. 4,806,856 by Hvezda et al is also of general interest in that it describes an adjustable test probe assembly having a spring loaded metal probe tip whose horizontal and vertical positions are independently adjusted by means of a mechanically complex probe support device. Hvezda et al employ a relatively rigid mounting arm for holding the spring-biased probe over the contact point. The probe assembly sits within a plate or other test assembly base. The Hvezda et al device incorporates a relatively complex and expensive arrangement to allow physical positioning of test probes relative to the contact points.
Also of interest is U.S. Pat. No. 4,123,706 by Roch. As with Hvezda et al, this patent is concerned with cantilever mounting of a contact by dual spring arms that position a needle-like contact on an electrical contact point in a circuit element under test. All three of the above-mentioned patents are concerned with test probes for attachment in multiple probe configurations in a generally surrounding relationship to an opening in a fixed frame plate so as to contact substrate points on a table below the mounting plate. In all cases, the contact point is moved up and down by the relative motion between the table containing the substrate and the frame holding the contact tips.
U.S. Pat. Nos. 4,847,553 by Seinecke, 4,956,923 by Pettingell et al and 5,075,621 by Hoyt all show various arrangements of cantilever-mounted contact probes for engaging contact points on a substrate in various configurations and with various enhancements. U.S. Pat. No. 4,403,822 by Smith shows a needle point contact which is arranged so as to have isolation in a gas-type seal configuration relative to the environment of a test board.
Generally speaking, prior art devices as exemplified above that are constructed and arranged to facilitate connection to circuit board test pads are mechanically complex and expensive to construct. While these devices may prove generally suitable for their limited intended purposes, the need remains for an inexpensive test probe that is of simple and reliable construction with general utility in situations where use of customized test stations, alligator clips or hand-held probes are impractical, too expensive, or simply not available.